Production of low alloy steel wire

ABSTRACT

Low alloy steel rod is given a pearlite structure and is then cold-drawn to initiate work hardening. The rod is then drawn through a die producing a reduction in area of between 10 and 40 percent. The wire leaving the die is heated to 300*-450*C and then forcibly cooled.

United States Patent 11 1 Stacey Oct. 29, 1974 1 PRODUCTION OF LOW ALLOYSTEEL 3,011,928 12/1961 Kopec et al l48/l56 WIRE 3,574,000 4/1971 Geipelet al 148/12 B 3,584,494 6/l97l Giepel et al 148/12 B Inventor: AndrewGordon y, Norton, 3,645,805 2/1972 Hoffman et al..... 148/124 nearDoncaster, England 3,711,338 1/1973 Vitelli 148/12.4

[73] Assignee: British Ropes Limited, Doncaster,

ng Primary Examiner-W. Stallard Attorney, Agent, or FirmJohnson,Dienner, Emrich, 22 F l d. N l 1 16 0v 1973 Verbeck & Wagner [21] Appl.No.: 416,203

[30] Foreign Application Priority Data [5 7] ABSTRACT Nov. 15, 1972Great Britain 52805/72 Low nd Steel rod is given a pearme structure d ithen cold-drawn to initiate work hardening. The rod is [52] US. Cl.148/12 B, 148/l2.4 then drawn through a die producing a reduction in [5l] ll lt. CI C2ld 9/52 area of between 0 and 40 percent h i l i [58]Field of Search 148/12 B, 12.4 the die is heated to 3 0 450 and then fibl cooled. [56] References Cited UNITED STATES PATENTS 5 Claims, NoDrawings 2,756,169 7/1956 Corson et al. l48/l2.4

1 PRODUCTION .01 LOW ALLOY STEEL WIRE The present invention relates tolow alloy steel wire.

The mechanical properties of drawn carbon-steel wire can be manipulatedand controlled by subjecting the wire to oil quench hardening andtempering. It would be desirable to be able to treat low alloy steel soas to'produce wire which has better mechanical'properties than oilquench hardened and tempered wire, espe- 2 (preferably 28 percent);heating the wire leaving the die to 300450C (preferably 420C andforcibly cooling the wire.

It can be seen that the reduction in area is low -40 percent); thetension on the wire leaving the die is only that needed to draw itthrough the die and does not necessarily produce permanent elongation;and the temperature to which the wire is heated is quite low (300-450CThe heat treatment to produce the pearlite structure lower relaxation-10 preferably comprises heating above the AC point, Great Britain Pat.No. 748,357 describes a method ofli to d h ldi t a temperature b tw 550treating cold drawn wire, in which the wire is drawn to d 700C hpreferred temperature b i 50C f its final Size in a die and, as 1631/65the 118,15 heated lowed by cooling in air. Of course, the heat treatedrod to a given temperature and then quenched, While it is will becleaned and given a drawing coat before the inisubjected to a tensilestress sufficient to induce permati l d wi pa s. nent elongation.According to Great Britain Patent No. Th i v ntio will be describedfurther, by way of ex- 5 the wife my be heat treated, before the fiample only, with reference to three steel compositions, drawingoperation, by heating the wire to above the viz. a carbon steel: 0.67percent Swedish carbon steel; AC point followed by isothermal quenchingto about and two low alloy steels: British Standard EN 47 75C.(chromium-vanadium) and EN 48a (silicon chro- Great Britain Patent No. l285 998 describes a mium). The analyses of the three steels are shown inmethod of making low-alloy steel wire, in which wire Table 1.

TABLE 1 Specification. wt% C Mn S P Cr V Si Swedish 0.65-0.80 0.40-0.800.040max 0.040max 0.35max EN 47 0.45-0.55 0.50-0.80 0.050max 0.050max0.50-0.80 0.15min 0.50max EN 48:: 0.50-0.00 0.00-0.90 0.050max 0.050max0.55-0.85 1.35-1.65

material is first given a heat treatment involving heating to atemperature 50-150C above the AC point, air cooling to just above the Mspoint, and reheating to 450-650C, followed by air cooling. Then followsmulti-hole cold drawing to the finished size, with a reduction in areaof at least 40 percent. The finished wire is tempered, preferably at440C or higher, without tensile stress or quenching. The steel has ahigh silicon content.

Neither of these methods is applicable to a wide range of low alloysteels.

The present invention provides a method of producing low alloy steelwire from low alloy steel rod, the method comprising heat treating therod to produce a pearlite structure; cold drawing the rod to initiatework hardening and thereby raise the tensile strength; drawing thepart-drawn rod through a drawing die to reduce As-rolled rod (5 mmdiameter) of each steel composition was initially austenitised, cooledto 650C and held at this temperature, and then allowed to cool in air;this provided a pearlite structure. The rod was cleaned, provided with adrawing coat, and drawn to a diameter of 4.4 mm; this initiated workhardening and raised the tensile strength.

The part-drawn rod was then further drawn, during which operation it wassubjected to a reduction in area of 25 percent, to finish at 3.85 mmdiameter. As soon as the wire emerged from the die, it was heated to420C and then quenched from this temperature by forcible cooling usingan air blast or water spray.

The resulting wire had a tensile strength ranging from 158 to 175 kgf/mmThe mechanical properties of the wire obtained from each steelcomposition are shown in Table 11. The properties of the as drawn wire(not the cross-sectional area by between 10 and 40 percent heated afterdrawing) are shown for comparison.

TABLE 11 WIRE Cr-V Cr-V as Si-Cr Si-Cr as 0.69% C. 0.69% C drawn drawnas drawn Size mm, 3.86 3.85 3.86 3.85 3.83 3 U'l'S kgf/mm 175.2 171.8166.0 158.9 170.0 176.5 (0.2 172.6 151.2 160.9 136.6 148.2 146.5 PS. (01171.5 138.7 158.5 123.3 146.2 128.8 (0.01 153.3 88.0 134.5 70.9 130.277.3 1. of P kgf/mm 132.5 68.7 106.8 53.7 112.8 58.0 P.S. (0.2 98.5 8896.8 85.9 87.0 82.7

as (0.1 UTS (0.01 87.6 51.2 81.0 44.6 76.4 43.8 L of P (7r UTS) 75.540.0 64.3 33.8 65.8 32.8 EXIO" 21.1 19.6 20.3 18.7 21.2 19.3 '71- E1.50mm 9.0 5.0 9.0 6.0 8.5 4.0 71' E1. 250mm 4.2 2.0 5.2 2.6 5.0 1.4 5 RofA 54. 56 58 49 53 Torsion on X 22 28 .27 42 25 33 dia.

TABLE ll-(ontinued WIRE Cr-V Cr-V as Si-Cr Si-Cr as 0.69% C. 0.69% Cdrawn drawn as drawn Torsion quality A A A A A A Bends on mm 8 l0 l3 l46 9 radius.

U'IS=ullimate tensile strength L of P=limil of proportionality R ofA=rcduction of area at fracture P.S=prool stress li=Youngs modulus Wirefrom all three steels shows a remarkable in- TABLE Ill-Continued creasein flow stress characteristics after the heat- Element weight% treatmentat 420C followed by quenching, the 0.2 per- 7 g 7 i I cent proofstresses are superior to those normally Vanadium (mo/2.00 achieved byoil hardening and tempering. l l- (mo/0'50 Niobium (HO/3.00 The resultsobtained for the low alloy steels are mg g 7 WA, H I nificantly betterthan those for the carbon steel. A posl claim,

sible explanation is that low temperature heat treatment under tensionmay promote a dislocation locking mechanism involving interstitialcarbon and nitrogen atoms, creating a condition similar to strainageing. Additions of such alloying elements as chromium, silicon, andvanadium, may promote an interaction between dislocations and alloycarbides, resulting in a further increase in flow stress.

Alloying elements which appear to have an influence on flow stress arelisted in Table lll together with the percentage ranges within which theinfluence appears to be significant.

Various modifications may be made within the scope of the invention. Forinstance, the rod can be given the pearlite structure by a heattreatment comprising controlled cooling of the rod as it leaves the hotrolling mill.

l. A method of producing low alloy steel wire from low alloy steel rod,the method comprising heat treating the rod to produce a pearlitestructure; cold drawing the rod to initiate work hardening and therebyraise the tensile strength; drawing the part-drawn rod through a drawingdie to reduce the cross-sectional area by between 10 and 40 percent;heating the wire leaving the die to 300450C; and forcibly cooling thewire.

2. A method as claimed in claim 1, in which the heat treatment toproduce a pearlite structure comprises heating above the AC point,cooling to and holding at a temperature between 550 and 700C, and thencooling in air.

3. A method as claimed in claim 2, in which the holding temperaturebetween 500 and 700C is 650C.

4. A method as claimed in claim 1, in which the heat treatment toproduce a pearlite structure is carried out on rod leaving a rollingmill.

5. A method as claimed in claim 1, in which the low alloy steel of whichthe rod is made contains, by weight:

C 0.30-1.00 percent, and alloying elements selected from the followingelements in the following ranges: Mn 0.20-l.50%, Si 0.l0-4.00%, Cr0.l04.00%, S 0.050% maximum, P 0.050% maximum, Mo 0.l02.00%, Cu0.l0-3.00%, Ni 0.l0-5.00%, Ti

v0.l02.00, V 2.00% maximum, N 0.50% maximum,

and Nb 0. l03.00%, the balance being Fe and impurities.

1. A METHOD OF PRODUCING LOW ALLOY STEEL WIRE FROM LOW ALLOY STEEL ROD,THE METHOD COMPRISING HEAT TREATING THE ROD TO PRODUCE A PEARLITESTRUCTURE, COLD DRAWING THE ROD TO INITIATE WORK HARDENING AND THEVEBYRAISE THE TENSILE STRENGTH; DRAWING THE PART-DRAWN ROD THROUGH A DRAWINGDIE TO REDUCE THE CORSSSECTIONAL AREA BY BETWEEN 10 AND 40 PERCENT;HEATING THE WIRE LEAVING THE DIE TO 300*-450=C; AND FORCIBLY COOLING THEWIRE.
 2. A method as claimed in claim 1, in which the heat treatment toproduce a pearlite structure comprises heating above the AC3 point,cooling to and holding at a temperature between 550* and 700*C, and thencooling in air.
 3. A method as claimed in claim 2, in which the holdingtemperature between 500* and 700*C is 650*C.
 4. A method as claimed inclaim 1, in which the heat treatment to produce a pearlite structure iscarried out on rod leaving a rolling mill.
 5. A method as claimed inclaim 1, in which the low alloy steel of which the rod is made contains,by weight: C 0.30-1.00 percent, and alloying elements selected from thefollowing elements in the following ranges: Mn 0.20-1.50%, Si0.10-4.00%, Cr 0.10-4.00%, S 0.050% maximum, P 0.050% maximum, Mo0.10-2.00%, Cu 0.10-3.00%, Ni 0.10-5.00%, Ti 0.10-2.00, V 2.00% maximum,N 0.50% maximum, and Nb 0.10-3.00%, the balance being Fe and impurities.